Surgical stapling devices have been in existence for many years. They are routinely used in surgical procedures mainly for the purposes of effecting a wound closure. Some of the most popular applications include closing a skin incision end-to-end or end-to-side anastomosis of internal (generally tubular) vessels such as the large bowel, etc. Current staplers are designed to deliver one or more staples in a serial fashion or a number of staples in one shot. Skin staplers, for example, deliver 30 or more staplers in a serial fashion. The staples are stacked within the device and during the firing operation one staple is advanced from the stack and delivered through the head of the device. During the following cycle another staple is advanced from the top of the stack and again delivered through the head of the device and so on. In one shot devices such as a bowel anastomosis stapler the staples are prearranged in a linear or circular fashion and upon activation of the device all the staples are delivered through the head. Examples of existing prior art as described above include U.S. Pat. Nos. 4,592,498, 5,289,963, 5,433,721 and 5,470,010.
The mechanism involved in forming a staple and releasing it from its forming mechanism is common to the majority of surgical stapler devices. Generally the components include an anvil, a staple closing actuator, and a staple release mechanism. The anvil is normally positioned in front of the staple and the actuator directly behind the staple. As the actuator advances the staple against the anvil the back section of the staple deforms around both ends of the anvil thereby transforming the staple from a generally U-shape to a generally rectangular shape. At this point the actuator generally retracts and the staple is released from the anvil either as a result of the anvil moving out of position and allowing the staple to move forward, or alternatively ejecting the staple over the anvil thereby releasing it from the device.
There are a number of problems associated with the mechanism as described above. Firstly, as the anvil is normally positioned in front of the staple it naturally becomes trapped between the back of the staple and the tissue into which it is being delivered causing the staple back to be spaced away from the tissue as opposed to lying tightly on its surface. This is a particular problem in the field of vascular puncture closure when it is desirable to keep the legs of the staple as short as possible so as to avoid having the legs of the staple within the vessel lumen.
Secondly, the method of releasing the staple from the anvil can be both complicated and unreliable. Metal springs are normally used which eject the staple over the anvil thereby affecting its release. However, should the spring fail to operate or is prohibited from operating properly by virtue of some tissue blockage etc, the device will become trapped in-situ.
Alternative release mechanisms include mechanical means of moving the anvil so that it is no longer in the path of the staple as it releases from the device. Again this generally involves very small metal components with relatively small movements which can fail to operate thereby leaving the staple trapped within the device and attached to the tissue into which it has been delivered.
Therefore there is a need for an improved surgical stapling device which will facilitate closer approximation of the staple back onto the surface of the vessel into which the staple is being delivered and a method of deforming the staple which does not include the use of an anvil component and therefore will not require the use of other components or mechanisms to facilitate the release of the staple from the anvil.